Features: Designed with voltmeter, voltmeter error is ±0.1V, measuring range is 5V~35V. Touch button switch changes measurement of input or output voltage, and there is indicator light shows which voltage is measured. Input and output have screw terminals for convenient connection even with no soldering iron, and keep solder pad for soldering connection. The maximum output current can be up to 4A; it is recommended that the working current in about 2A, and add heat sink please if more than 2A. Using the internal oscillation frequency of 400kHz, belong to second generation of the switch voltage regulator, low consumption, high efficiency. Widely used for storage battery, power transformers, DIY adjustable regulated power supply, industrial equipment, 9 to 12V, 12V to 18V, 18V to 24V, etc. Specifications: Input Voltage: 4.5V-32V Output Voltage: 5V-35V (adjustable) Max. Output Current: 4A Efficiency: <92% Output Ripple: <30mV Switch Frequency: 400kHz Operating Temperature: -40℃~+85℃ Size: Approx. 66 x 36 x 14mm/2.59 x 1.41 x 0.55" Instruction: 1. For the first time powering on, the default display is input voltage, and the input indicator IN lights up.Press the button, then it displays output voltage, and the output indicator OUT lights up.The last setting will be saved, even if power off and restart. 2. Input output voltage measurement error calibration:Press and hold button switch for more than 4 seconds then release to enter voltage measurement error calibration function, indicator IN lights up(input voltage calibration), and display flickeringly shows calibration value (default is 0.0). Press button to change this value (range of -0.5V to 0.5V)After adjustment of the input voltage calibration value, press and hold button for more than 2 second then release to enter the output voltage error calibration function, indicator OUT lights up (output voltage calibration), and display calibration value. Adjustment method is the same as the input adjustment. After adjustment, press and hold button for more than 2 seconds then release to save set value and return normal voltage displaying.The calibration value is enabled immediately and saved when power failure.(This function can provide higher accuracy) 3. Turn off the voltmeter:Press and hold switch for more than 1 second while less than 4 seconds then release to turn off voltmeter.Voltmeter will be turned on if press switch after it is turned off. Note: 1. If input voltage is lower than 4.5V, the voltmeter will not work and display. 2. Input voltage must be at least 1V higher than output voltage. 3. When power is over 20W, a heat sink is recommended to enhance heat dissipation. 4. If output voltage is always equals to input voltage and cannot be adjusted,turn potentiometer more than 10 circles counterclockwise please, then voltage can be adjusted normally. 5. Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering. Package Includes: 1 x Boost Converter Module .